Spatial variability of inorganic nutrients and physical parameters in the waters of Bahia Magdalena lagoon, Pacific Coast, Mexico

Abstract Seventy-seven water samples were collected at the surface (S) and bottom (B) water profiles along eight transects (T1–T8) from Bahia Magdalena lagoon, Baja California Sur, Mexico during October 2014 to evaluate the spatial distribution patterns of dissolved inorganic nutrients (nitrates, nitrites and phosphates). Sea water properties (pH, temperature, dissolved oxygen, salinity, density and conductivity) were measured using a CTD instrument to assess their vertical profiling. On average, the lagoonal waters perceived raised temperatures (28.98 °C) and salinities (35.2 PSU) due to its semi-arid environmental setting. The lagoon presented an average pH value of 8.25 due to the high influence of sea water under oxygenated conditions. Due to the impact of wind driven waves and ventilation process, high oxygen saturation value of 96.8% (avg.) was observed in the waters. The average inorganic nutrient levels in the lagoon (nitrites: 0.002 mg/L, nitrates: 0.033 mg/L, phosphates: 0.023 mg/L) is due to the distinctive biogeochemical lagoon processes namely reduced precipitation, upwelling and absence of river input. The present study provides a preliminary data on the hydrographical and nutrient characteristics of a highly productive lagoon on the western coastal margin (Mexico) of the Pacific Ocean.